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<p>The present work discusses novel alumina composites with single crystalline α-alumina platelets as reinforcement, fabricated by integrating gelcasting with rapid prototyping technique. Commonly used alumina fibre reinforced composites, though exhibit high fracture toughness, show limitation for use at high temperatures, due to structural transformation and recrystallization of the fibres, and for net-shaping into intricate geometries. Present work addresses these constraints by choosing α-alumina platelets of approximately 150 ± 25&#xa0;nm thickness as reinforcement, and gelcasting process for shape-forming the composites. A free-flowing ceramic slurry having uniform distribution of monazite (LaPO<sub>4</sub>)-coated platelets was cast and gelled in disposable expanded polystyrene (EPS) molds that are machined as per the computer aided design (CAD). The green bodies are dried, debindered and sintered to obtain compacts of alumina composites with different amounts of platelet alumina (0 to 25 wt%) and are characterized. Compared to monolithic alumina, a notable enhancement (by 80%) to 5.4 MPa<InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\:\surd\:m\)</EquationSource> </InlineEquation> in fracture toughness was observed, while maintaining a flexural strength of 310&#xa0;MPa, in the composite with 4 wt% platelet content. Microstructural studies reveal deflection, bridging, and branching of the cracks caused by the coated platelets and provide evidence for their contribution to improved fracture toughness. The optimized composites have the potential for use in biomedical sector. They are particularly suitable for high-temperature applications, furthermore, α-alumina platelets possess superior thermal stability at elevated temperatures compared to alumina fibres and exhibit excellent oxidation resistance, unlike carbon fibres. These attributes ensure their structural integrity under extreme conditions, making them highly effective as reinforcements for high-temperature applications where both mechanical performance and environmental durability are critical. The present process is inexpensive and enables manufacturing of complex geometries, making it attractive for adoption by industries.</p>

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Enhanced fracture toughness by α-alumina platelets in alumina composites net shaped by gelcasting into RPT molds

  • 期刊论文

  • 发表日期：

    2025年5月30日

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  • Jeevankumar Pallagani,
  • Poly Rose,
  • Rajanikanth Ammanabrolu,
  • Seshu Bai Vummethala,
  • Rajasekharan Thankappan Pillai

摘要

The present work discusses novel alumina composites with single crystalline α-alumina platelets as reinforcement, fabricated by integrating gelcasting with rapid prototyping technique. Commonly used alumina fibre reinforced composites, though exhibit high fracture toughness, show limitation for use at high temperatures, due to structural transformation and recrystallization of the fibres, and for net-shaping into intricate geometries. Present work addresses these constraints by choosing α-alumina platelets of approximately 150 ± 25 nm thickness as reinforcement, and gelcasting process for shape-forming the composites. A free-flowing ceramic slurry having uniform distribution of monazite (LaPO4)-coated platelets was cast and gelled in disposable expanded polystyrene (EPS) molds that are machined as per the computer aided design (CAD). The green bodies are dried, debindered and sintered to obtain compacts of alumina composites with different amounts of platelet alumina (0 to 25 wt%) and are characterized. Compared to monolithic alumina, a notable enhancement (by 80%) to 5.4 MPa \(\:\surd\:m\) in fracture toughness was observed, while maintaining a flexural strength of 310 MPa, in the composite with 4 wt% platelet content. Microstructural studies reveal deflection, bridging, and branching of the cracks caused by the coated platelets and provide evidence for their contribution to improved fracture toughness. The optimized composites have the potential for use in biomedical sector. They are particularly suitable for high-temperature applications, furthermore, α-alumina platelets possess superior thermal stability at elevated temperatures compared to alumina fibres and exhibit excellent oxidation resistance, unlike carbon fibres. These attributes ensure their structural integrity under extreme conditions, making them highly effective as reinforcements for high-temperature applications where both mechanical performance and environmental durability are critical. The present process is inexpensive and enables manufacturing of complex geometries, making it attractive for adoption by industries.